(1) Field of the Invention
The present invention relates to an apparatus and a method for removing sludge sediment from a waste sewage containment reservoir. In particular, the present invention relates to a sludge scraper apparatus that can be easily moved over a waste sewage containment reservoir for scraping sludge sediment from the bottom of the reservoir. The apparatus has a main frame that mounts a scraper blade at one end and a pair of skids at an opposite end of the frame. A set of wheels are journaled to an axle that is mounted on the frame at an intermediate position between the ends of the frame. A first tow line is mounted on the one end of the frame, adjacent to the scraper blade, and is connected to a first winch mounted on a first shore of the reservoir. A second tow line is mounted on the skids and is connected to a second winch mounted on a second shore of the reservoir. The sludge scraper apparatus removes sludge sediment from the reservoir by cycling in passes over the bottom of the reservoir. A pass begins with the sludge scraper apparatus adjacent to the second shore. The first winch then spools up the first tow line, which causes the scraper blade to move over the bottom of the reservoir, plowing sludge sediment towards the first shore. Once the scraper apparatus has reached the first shore, the second winch is actuated to spool up the second tow line. This causes the sludge scraper apparatus to rotate on the wheels in a first direction with the scraper blade rotating off the bottom of the reservoir so that the skids are positioned in contact with the bottom of the reservoir. In this position, the sludge scraper apparatus is able to be pulled back towards the second shore by the second winch, moving over the bottom of the reservoir on the skids and the wheels. Once the scraper apparatus reaches the second shore, the first winch is again actuated, which causes the sludge scraper apparatus to rotate on the wheels in a second direction, opposite the first direction, so that the scraper blade contacts the bottom of the reservoir for another pass. The first and second winches are moved along the shore, preferably a distance equal to the swath of the scraper blade. This repositions the sludge scraper apparatus for another cycle This process is repeated until the sludge sediment has been plowed from the bottom of the reservoir and piled up adjacent to the first shore The accumulated sludge sediment can then be removed from the reservoir by a power shovel or any other suitable means.
(2) Prior Art
The prior art has described various types of apparatus for removing sludge sediment from a sludge sedimentation tank. Sedimentation tanks are rigid vessels that are usually constructed of concrete or metal to form the tank. Two general types of scraper apparatus are used to remove sludge sediment that has precipitated onto the bottom of the tank. The first type has a track or guide rail that extends across the top of the tank. A scraper apparatus rides back and forth on the rail by means of a motor or a pulley system driven by a motor. The scraper apparatus has a scraper blade that extends towards the bottom of the tank. When the scraper apparatus moves in a forward pass, the scraper blade is caused to plow sludge sediment off the bottom of the reservoir and preferably towards a sludge hopper located at one end of the tank. The scraper apparatus then moves backwards, towards the opposite end of the tank to a position ready for another forward pass. When the scraper apparatus travels in the backwards direction, the scraper blade preferably moves into a retracted position to help the backwards movement of the scraper apparatus. Illustrative of this first type of sludge scraper apparatus is U.S. Pat. Nos. 2,009,559 to Mieder; 2,033,291 to Laughlin et al; 2,101,080 to Lund; 3,410,412 to Fechter and 4,417,983 to Smigerski et al.
The second type of sludge sediment scraper apparatus moves over the bottom of the tank powered by a pulley system. The scraper apparatus is preferably provided with wheels that ride over the concrete or metal bottom of the tank. A scraper blade is positioned adjacent to the bottom of the tank as the scraper apparatus plows in a forward direction, towards a sludge hopper. On the return trip back across the bottom of the tank, the scraper blade is retracted. This second type of apparatus works well as long as the bottom of the tank is rigid enough to support the weight of the scraper apparatus. Illustrative of this type of sludge scraper apparatus is U.S. Pat. Nos. 1,918,742 to Elrod; 1,919,689 to Elrod and 4,724,088 to Zetterlund.
All the prior art sludge scraper apparatus are designed to remove sludge from sedimentation tanks that are rigid containment vessels, made from metal or concrete.
What is not shown by the prior art is a sludge scraper apparatus that is useful for removing sludge sediment from a sludge containment reservoir having a loose, earthen bottom. The prior art apparatus did not encounter the problem of removing sludge sediment from an earthen reservoir, so there was never the need to invent a scraper apparatus that can slide across the bottom of a sludge reservoir. Therefore, even though the scraper apparatus of the present invention can be used to remove sludge sediment from all types of waste sewage reservoirs and tanks, the present invention is particularly useful in sludge reservoirs having earthen bottoms. Earthen reservoir bottoms are usually made of clay or peat as a means of containing the liquids comprising the waste sewage, and clay or peat reservoir bottoms tend to be relatively soft and unconsolidated. This prohibits the use of heavy plowing equipment, such as bulldozers and apparatus similar to those shown by the prior art, which easily become bogged down in the loose sludge sediment and clay or peat.
The problem is therefore to provide a scraper which operates well in the setting where the reservoir has a bottom which is made of clay or peat. The prior art apparatus are not suitable for this setting.